A cube corner type retroreflector, for example, that shown and described in the Heenan et al U.S. Pat. No. 3,541,606, which incorporates two or three retroreflective areas, each area being comprised of a group of discrete reflector elements or units, each group having members with similar respective optical axes which are disposed collectively at an angle which differs from the corresponding angle in each of the other groups, suffers from the disadvantage that the total retroreflective surface region thereof has necessarily heretofore been comprised of such groups, and the total area each group occupies comprises a relatively large percentage of the total retroreflective surface region of such a given cube corner type reflector. Thus, if perchance a portion of the surface area of an individual retroreflector utilizing two or three such different groups of reflector elements therein is partially covered over as by a foreign body, so that, for example, the surface area occupied by one group of reflector elements is rendered non-functional, that reflector body itself is no longer fully retroreflective of light incident thereagainst, and thus that retroreflector is not retroreflective at the angles and to the extent previously served by the uncovered groups of retroreflector elements. This result, as a practical matter, can be regarded as having serious safety consequences, particularly in the area of reflectorized vehicles, such as bicycles, which are equipped with reflectors having multiple groups of discrete reflector elements. For example, a bicycle equipped with a reflector having two or three different groups of cube corner reflector elements therein, as indicated above, may no longer be seen by, for example, a motorist approaching such so equipped moving vehicle at night from an angle of from about 40.degree. to 70.degree., for example, if such reflector's wide angle groups are obscured by spatter of road mud, or the like. Consequently, in cube corner reflector art, there is a need for a cube corner type retroreflector having two or more different groups of discrete cube corner reflector elements therein comprising the entire retroreflective region with each group having its members with similar respective optical axes which are disposed at different angles as taught in the prior art, but wherein the individual members of these groups are so-distributed and so-intermixed across the entire retroreflective region of such reflector that a partial obscuring of that reflector's retroreflective region does not stop completely the generation of a desired, designed pattern of light retroreflection intended to be achievable with such reflector.
Because cube corner type retroreflectors comprised of molded transparent solid material have heretofore characteristically been manufactured from molds having incorporated thereinto, as the molding surface for forming cube corner retroreflective units, monolithic electroforms made from entire groups or clumps of facetted pin bundles wherein in individual pins are appropriately facetted and arranged so as to produce an electroformable surface incorporating a plurality of discrete reflector units, it is heretofore not been possible to produce retroreflectors of the class indicated above wherein two or more different groups of cube corner retroreflector elements are disposed over the entire region of such reflector. Thus, as those skilled in the art of cube corner reflector manufacture will know, molds for cube corner retroreflective reflectors are prepared by a manufacturing sequence in which tiny pins, which commonly can be hexagonally shaped, having like facets formed at a forward end of each pin, are grouped into a pattern or bundle. The faceted pin ends of the bundle then serve as a form or surface upon which an electroform mold is made. Electroform molds are currently made by electroplating nickel or the like onto and over a pin bundle so that, in such process, all points, including the high points and the low points thereof, respectively, over such a group of pins are reversed in exact mirror immage fashion in the product electroform over their respective locations in the pin bundle. Then, using the product electroform, a mold is made in which transparent plastic reflectors are moldable. Because of the small size of the individual cube corner retroreflective units in such an electroform, and also because of cube corner retroreflective unit geometries, it has heretofore been necessary in the manufacture of molds for making cube corner retroreflectors to employ individual electroform structures wherein all of the discrete cube corner retroreflective units therein comprising a region of retroreflective faceted units have optical axes disposed substantially parallel to one another. Then, in the process of making a completed mold, having two or three different groups of retroreflective areas, several different types of separately formed electroform structures are mounted together usually and typically in an adjoining, adjacent relationship, each individual such electroform structure being comprised of a plurality of cube corner retroreflective units wherein the optical axes are respectively disposed parallel to one another, thereby to achieve a reflector of the character as described, for example, in the aforementioned Heenan et al U.S. Patent.
It has recently been discovered that electroform construction or equivalent, such as above described, can be transversely sliced or cut up, as with a metal saw or the like, into a plurality of elongated slab-like bodies, each one having spaced, generally parallel respective side walls with connecting edge walls and end walls. This slicing is conductable in such a manner that, in each slab-shaped body, one edge wall thereof has defined therein a plurality of cube corner retroreflective units arranged in a row which extends lengthwise along and in the face of such one edge wall. The individual slab-shaped bodies which result are then adapted to be mounted together in a side-by-side, preferably aligned, relationship into a block so as to provide a desired region of cube corner retroreflective units. By interposing in some chosen appropriate manner in adjacent side by side relationship to one another different slab-shaped bodies, a wide variety of patterns of cube corner type retroreflective units can be produced, and mold assemblies can be fabricated incorporating such a resulting block. See my copending application filed on even date herewith (identified by U.S. Ser. No. 699,959, filed June 25, 1976), the teachings of which are incorporated by reference into the present specification.